Passenger airbags in which a diffuser is installed in an airbag main body to control the flow of gas from an inflator are described in Japanese Unexamined Patent Application Publication No. 11-198750 and Japanese Unexamined Patent Application Publication No. 10-71904. In Japanese Unexamined Patent Application Publication No. 11-198750, the flow direction of gas from an inflator is controlled in the left-right direction by a diffuser. In Japanese Unexamined Patent Application Publication No. 10-71904, gas discharge openings provided in a diffuser (referred to as “inner bag” in Japanese Unexamined Patent Application Publication No. 10-71904) face not straight toward the rear of the vehicle but obliquely upward and downward or obliquely leftward and rightward so that the airbag inflates softly for a front-seat passenger or a child in front of them. In this specification, “left-right direction” corresponds to the left-right direction of the vehicle body. “Left” and “right” are the left and right from the perspective of a front-seat passenger.
In Japanese Unexamined Patent Application Publication No. 11-5505, it is described that the inside of an airbag is divided into two upper and lower parts with a tether, and when the airbag interferes with an interfering object during the inflation of the airbag, gas in the upper part is caused to flow to the lower part through both left and right sides of the tether to reduce the impact on the interfering object.                PTL 3: Japanese Unexamined Patent Application Publication No. 11-5505        